Preparation of pyrrolines by the amination of ketones

ABSTRACT

Nitrogen-containing heterocyclic compounds having five ring atoms are prepared by the vapor phase reaction of olefinic ketones with ammonia at elevated temperatures and in the presence of a porous metal oxide catalyst.

United States Patent [191 Metz et al. June 17, 1975 PREPARATION OF PYRROLINES BY THE [56] References Cited AMINATION OF KETONES UNITED STATES PATENTS [75] Inventors: Fred L. Metz, Painesville; James A. 3,259,632 7/1966 Fremery 260/3131 Scozzie, Wickliffe, both of Ohio I Primary Examiner-Joseph A. Narcavage [73] Assignee' 21:33:: g gg Corporahon Attorney, Agent, or FirmTimothy E. Tinkler [22] Filed: Feb. 21, 1973 [57] ABSTRACT [21] Appl. No.: 334,235 Nitrogen-containing heterocyclic compounds having five ring atoms are prepared by the vapor phase reaction of olefinic ketones with ammonia at elevated temperamres and in the presence ofa porous metal oxide 581 Field of Search 260/3131 catalyst 8 Claims, No Drawings PREPARATION OF PYRROLINES BY THE AMINATION OF KETONES BACKGROUND OF THE INVENTION A number of five-membered nitrogen-containing heterocycles are known that are useful as the compounds per se or as intermediates. particularly for the synthesis of biologically active compounds. The various synthetic productions of these heterocycles can involve addition reactions. replacement of substituents on a preformed ring, or ring closure. Exemplary of the latter is the reaction of a l,4-dicarbonyl compound. e.g., 2.5- hexanedione, with ammonia to yield 2,5- dimethylpyrrole. Such reactions are not generally commercially practical, however. since the requisite 1.4- dicarbonyl compounds are not readily available.

STATEMENT OF THE INVENTION Therefore, it is an object of the present invention to provide a simple process for the production of heterocyclic compounds.

It is a further object of the present invention to provide a simple process for the production of heterocyclic nitrogen-containing compounds from commercially available or readily synthesized reactants.

These and further objects of the present invention become apparent to those skilled in the art from the specification and claims that follow.

There has now been found a process for the production of heterocyclic organic compounds having a fivemembered nitrogen-containing heterocyclic ring, which process comprises reacting an olefmic ketone having at least two carbon atoms between the carbonyl carbon and the double bond with ammonia at a temperature between about 300 and 600 C in the presence of a porous metal oxide catalyst. More specifically, a ketone having the formula:

wherein R is aliphatic or aromatic; R is H or R; Z is cycloalkanone; n is l or 2; and m is or 1, is reacted with an excess of ammonia at a temperature between about 300 and 600 C in the presence of a porous metal oxide catalyst. This process is particularly useful for the reaction of olefinic ketones with ammonia in the presence of porous alumina. Owing to the variety of olefinic ketones that may be employed as reactants, it is possible by this process to tailor make a large number of five-membered nitrogen-containing heterocycles, both substituted and unsubstituted, by selection of the proper ketone. Further, the reaction can be made to proceed with good conversion of the ketone and a high selectivity to the desired product.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of the present invention is applicable to the conversion of a wide variety of olefinic ketones. substituted and unsubstituted. into five-membered nitrogen-containing heterocycles. Ketone precursors are also contemplated. Most of these ketones correspond to formulas:

wherein R is a substituted or unsubstituted aliphatic or aromatic radical. preferably a C -C aliphatic radical; R is H or R; Z is cycloalkanone; n is l or 2; and m is 0 or 1. Since closure is effected between the carbonyl carbon and, through the added nitrogen, the gamma carbon atom, it will be apparent that any remaining groups become substituents on the heterocyclic ring.

Illustrative of these ketones and the heterocyclic products oftheir reaction with ammonia are the followcit ,cn=cncH cn coca en cn cn=caca cocn Y I I H 0 CH3 3 Pressures employed are generally atmospheric. although values within the range of 0.5 to 25, especially 0.5 to 7.0. atmospheres are useful.

The temperature at which the reaction proceeds is In order that those skilled in the art may more readily understand the present invention and certain preferred embodiments by which it may be carried into effect. theft'illowing specific examples are afforded.

able, relatively pure, aluminas at temperatures in excess of 1 100 C, for example, up to l300 C. These sintered metal oxides are found to have the requisite porosity and, in the preferred case of alumina. a high alpha-alumina content.

generally within the, range of 300-600 C, the exact temperature depending upon a number of eonsider- EXAMPLE 1 ations such as the identity of the ketone. the contact time within the re r. h cti ity f h atalyst. and The reaction is conducted in a tubular heated reactor the like. A preferred temperature range is between (460 C) provided with a preheating zone (300 C) for 400 and 550 C. in the instance wherein the ketone is It) h rcdctums above a fi d nn b d d a d i allylacetone. it temperature Within 11 a g cooled condenser on the outlet to collect both reaction C 15 especially to prcfcrrcdht most products and excess ammonia. Ammonia and allylacestances, 1t w1ll be found desirable to preheat the reac- {one are f d t d mix d i th t f id r t i tants to a temperature approaching that at which the a mole r tio f33;1 and at a rate of grams per hour reaction proceeds. of allylacetone. The reactants pass downward at sublh Order t0 avmd'tleiomposltloh p h at the stantially atmospheric pressure through 200 ml of granvated temperatures mvolved, the reaction time is prefl l h l i Candy 99% through a 5 US erably quite Short. 8-g-, between 1 11nd 866M105, Standard mesh screen, 98% on an 8 mesh screen). This P shcohdh although longer times have been catalyst has a pore volume of 0.60 ml/gram, a surface employed- Thts will depchd P the tcmpetuturc area of about 10.5 square meters/g (measured by the of the reactor, the identity of the ketone reactant and BET thod, nitrogen adsorption), a density of 0.64 product obtained, and the like. g/ml, and has been presintered for 2 hours at l200 C.

The amount of ammonia p y is at least the Catalyst-reactant Contact time is 3.9 seconds on the avoretical stoichiometric quantity required to react with ge, The excess ammonia is recycled to provide a t ketone to Provide the desired P P continuous process. In this manner, 99.3 of the allyh w v r. 2 x -g-. cnf l n laeetone is converted with a selectivity of 73.4% to preferably even a twentyfold or greater excess. is ent- 2,5-dimcthyl-l-pyrroline, ployed, The use of such large amounts apparently con- The following table shows a variation in certain of'tbe tributes to the specificity of the reaction of the ketone r i parameters and h r lt th reb b i d, to the desired product without decompositio Of the still employing allylacetone the ketone reactant and starting material. Any unreacted ammonia is, of course, obt i in 2,5-di thyl-l-pyrroline as the product. All easily recovered. reaction parameters unstated in'the table are de- The catalysts required to effect the desired selective tailed above. The catalyst differs in having been preconversions are generally described as particulate poheated at 1200 C for 3 hours and having a surface area rous metal oxides, for example, thoria, tungsten oxide, of l 1.4 m /g, a density of 0.65 g/ml, and a pore volume molybdenum oxide,- kieselguhr, nickel oxide, cobalt oxof 0.60 ml/g.

TABLE Reaction 'ALA Catalyst Vol. Temperature Time Conversion Selectivity Run (g/hr) NH;;:ALA (ml) (C) (sec) ("/1) 7!) 1 6 58:1 140 460 2.7 98.5 62.0 2 10 :1 225 440 3.4 99.0 62.7 3 10 33:1 200 440 3.8 98.9 65.3 4 6 30:1 I40 420 5.5 87.5 55.4 5 20 261i 200 455 2.4 95.] 62.5 6 l2 251l 200 435 4.0 92.0 56.9 7 [0 24.1 141) 460 3.6 94.0 58.9 8 10 17:1 140 420 5.4 71.8 41.5 9 20 10:1 201) 461 3.7 99.0 54.7 I0 20 133i 200 445 5.l 96.1 47.4

ALA allylacetone ide, zirconia, and alumina. A high degree of porosity. EXAMPLE 2 4 1 v I ml/grflm preffrlbly 05 9 5g The reaction of Example 1 is again repeated employapparently essenttal to selective conversion. Part1cumg lanylcyclohcxamme as the ketone NH3 and the larly preferred i e a l fi g 9 ketone (33:1) are preheated to about 380 C and fed convelsm? f e56 5 ygts through the reactor at a temperature of 450 C, with a are usbfu m pdfncu pow 9 contact time of 3.6 seconds and at a rate of 10 g ketom preferably m Glider to pr,evem ohreduce cmmm' ne/hour. At a 95% rate of conversion, the fused ring of the Catalyst m the Vapors exiting the t nitrogen-containing hcterocyclic product is obtained as 1n the form of catalyst pellets prepared by compacting the ma or product. a more highly particulate metal ox1de. Preferred catalysts having the desired properties may be readily obtained, for example, by sintering commercially avail- 6g EXAMPLE lllustrating the use of a porous metal oxide catalyst other than alumina. /3 inch pellets of 98% zirconium oxide and 2% alumina having a pore volume of 0.2 ml/g, are employed after sintering for 3 hours at l l wherein R is a C -C, aliphatic radical; R is H or R; and n is 1 or 2, with (B) an excess of NH3 at a temperature between 400 and 550 C in the presence of a sintered, high porosity, alumina.

2. A process as in cliam 1 wherein the aluminacontaining catalyst has been sintered at a temperature in excess of 1 100 C.

3. A process as in claim 1 wherein at least a tenfold excess of NH is employed.

4. A process as in claim 1 wherein the alumina has a pore volume of at least 0.5 ml/g.

5. A process for the production of 2,5-dimethyl-1- pyrroline, which process consists essentially of reacting allylacetone with an excess of ammonia at a temperature between about 400 and 500 C in the presence of a particulate, high porosity, alumina catalyst.

6. A process as in claim 5 wherein the catalyst is alumina sintered to in excess of 1100. C.

7. A process for the production of 2,5-dimethyl-1- pyrroline with a selectively greater than about 40 percent, which process consists essentially of reacting NH and allylacetone in a mole ratio of at least 10:1 and at a temperature between about 440-480 C for from about 2-5 seconds in the presence of a particulate, high porosity, alumina.

8. A process as in claim 7 wherein the alumina has been sintered at a temperatue in excess of 1 C. 

1. A PROCESS FOR THE PRODUCTION OF A SUBSTITUTED PYRROLINE, WHICH PROCESS COMPRISES REACTING (A) A KETONE HAVING THE FORMULA*
 2. A process as in cliam 1 wherein the alumina-containing catalyst has been sintered at a temperature in excess of 1100* C.
 3. A process as in claim 1 wherein at least a tenfold excess of NH3 is employed.
 4. A process as in claim 1 wherein the alumina has a pore volume of at least 0.5 ml/g.
 5. A process for the production of 2,5-dimethyl-1-pyrroline, which process consists essentially of reacting allylacetone with an excess of ammonia at a temperature between about 400* and 500* C in the presence of a particulate, high porosity, alumina catalyst.
 6. A process as in claim 5 wherein the catalyst is alumina sintered to in excess of 1100* C.
 7. A process for the production of 2,5-dimethyl-1-pyrroline with a selectively greater than about 40 percent, which process consists essentially of reacting NH3 and allylacetone in a mole ratio of at least 10:1 and at a temperature between about 440*-480* C for from about 2-5 seconds in the presence of a particulate, high porosity, alumina.
 8. A process as in claim 7 wherein the alumina has been sintered at a temperatue in excess of 1100* C. 